1. Field of the Invention
The present invention relates to the field of lifting devices. More particularly, this invention relates to a mechanism for preventing a lifting device from tipping over when a pothole, bump, curb or other support threatening and tip generating hazard is encountered. This invention is extremely useful on a mobile scissor lift which tends to develop an increased potential tipping moment as the lift is raised.
2. Problems in the Art
Various lifting devices have been developed to raise material and/or workers to elevated locations. However, many of these devices are subject to a potential problem which is as old as the ladder itself--they can tip over under certain conditions. Generally, the higher the lifting device reaches, the greater the moment arm and therefore the greater the chances of the machine overturning.
Many modern lifting devices are mobile and some are even self-propelled. While these features enhance the flexibility and usefulness of the lifting devices, the resulting acceleration and deceleration add to the tipping problem. Furthermore, environmental factors including wind and road conditions often contribute to the possibility of tipping. One or more wheels of a mobile lifting device may hit a pothole or run into (or fall off of) a curb, leading to an increased tipping moment. In devices like scissor-style personnel lifts (some of which are also known as MEWP's, mobile elevating work platforms) where the operator is suspended high in the air, tipping can be a serious concern.
Some conventional lifting devices have additional supports, braces, or stabilizing legs which extend diagonally outward from the main frame to contact the ground. However, such braces increase the area consumed by the machine during its operation and decrease machine mobility because the braces generally must be retracted before moving the machine. Furthermore, the feet on the stabilizing legs present a relatively small surface area to the ground for stabilization.